In the 1920s, shortly after the discovery of bacterial viruses (bacteriophages), the medical community began to extensively pursue the treatment of bacterial diseases with bacteriophage therapy. The idea of using phage as a therapy for infectious bacterial diseases was first proposed by d'Herelle in 1918, as a logical application of the bacteriophages' known ability to invade and destroy bacteria. Although early reports of bacteriophage therapy were somewhat favorable, with continued clinical usage it became clear that this form of therapy was inconsistent and unpredictable in its results. Disappointment with phage as a means of therapy grew, because the great potential of these viruses to kill bacteria in vitro was not realized in vivo. This led to a decline in attempts to develop clinical usage of phage therapy, and that decline accelerated once antibiotics began to be introduced in the 1940s and 50s. From the 1960s to the present, some researchers who adopted certain bacteriophages as a laboratory tool and founded the field of molecular biology have speculated as to why phage therapy failed.
Despite the general failure of phage as therapy, isolated groups of physicians have continued to try to use these agents to treat infectious diseases. Many of these efforts have been concentrated in Russia and India, where the high costs of and lack of availability of antibiotics continues to stimulate a search for alternative therapies. See for example Vogovazova et al., "Effectiveness of Klebsiella pneumoniae Bacteriophage in the Treatment of Experimental Klebsiella Infection", Zhurnal Mikrobiologii, Epidemiologii Immunobiologii, pp. 5-8 (April, 1991); and Vogovazova et al., "Immunological Properties and Therapeutic Effectiveness of Preparations of Klebsiella Bacteriophages", Zhurnal Mikrobiologii, Epidemiologii Immunobiologii, pp. 30-33 (March, 1992)]. These articles are similar to most of the studies of phage therapy, including the first reports by d'Herelle, in that they lack many of the controls required by researchers who investigate anti-infectious therapies. In addition, these studies often have little or no quantification of clinical results. For example, in the second of the two Russian articles cited above, the Results section concerning Klebsiella phage therapy states that "Its use was effective in . . . ozena (38 patients), suppuration of the nasal sinus (5 patients) and of the middle ear (4 patients) . . . In all cases a positive clinical effect was achieved without side effects from the administration of the preparation". Unfortunately, there were no placebo controls or antibiotic controls, and no criteria were given for "improvement".
Another clinical use of phage that was developed in the 1950s and is currently still employed albeit to a limited extent, is the use of phage lysate, specifically staphphage lysate (SPL). The researchers in this field claim that a nonspecific, cell-mediated immune response to staph endotoxin is an integral and essential part of the claimed efficacy of the SPL. [See, eg., Esber et al., J. Immunopharmacol., Vol. 3, No. 1, pp. 79-92 (1981); Aoki et al., Augmenting Agents in Cancer Therapy (Raven, New York), pp. 101-112 (1981); and Mudd et al., Ann. NY Acad. Sci., Vol. 236, pp. 244-251 (1974).] This treatment, it seems that the purpose of using the phage is to lyse the bacteria specifically to obtain bacterial antigens, in a manner that those authors find preferential to lysing by sonication or other physical/chemical means. Here again, some difficulties arise in assessing these reports in the literature, because, in general, there are no placebo controls and no standard antibiotic controls against which to measure the reported efficacy of the SPL. More significantly, there is no suggestion in these articles to use phage per se in the treatment of bacterial diseases. Moreover, the articles do not suggest that phage should be modified in any manner that would delay the capture/sequestration of phage by the host defense system.
Since many patients will recover spontaneously from infections, studies must have carefully designed controls and explicit criteria to confirm that a new agent is effective. The lack of quantification and of controls in most of the phage reports from d'Herelle on makes it difficult if not impossible to determine if the phage therapies have had any beneficial effect.
As there are numerous reports of attempts at phage therapy, one would assume that had it been effective, it would have flourished in the period before antibiotics were introduced. But phage therapy has been virtually abandoned, except for the isolated pockets mentioned above.
As noted above, some of the founders of molecular biology who pioneered the use of specific phages to investigate the molecular basis of life processes have speculated as to why phage therapy was not effective. For example, G. Stent in his book Molecular Biology of Bacterial Viruses, WH Freeman & Co. (1963) pp. 8-9, stated the following:
"Just why bacteriophages, so virulent in their antibiotic action in vitro, proved to be so impotent in vivo, has never been adequately explained. Possibly the immediate antibody response of the patient against the phage protein upon hypodermic injection, the sensitivity of the phage to inactivation by gastric juices upon oral administration, and the facility with which bacteria acquire immunity or sport resistance against phage, all militated against the success of phage therapy."
In 1973, one of the present inventors, Dr. Carl Merril, discovered along with his coworkers that phage lambda, administered by various routes (per os, IV, IM, IP) to germ-free, non-immune mice, was cleared out of the blood stream very rapidly by the organs of the reticulo-endothelial system, such as the spleen, liver and bone marrow. [See Geier, Trigg and Merril, "Fate of Bacteriophage Lambda in Non-Immune, Germ-Free Mice", Nature, 246, pp. 221-222 (1973).] These observations led Dr. Merril and his coworkers to suggest (in that same Nature article cited above) overcoming the problem by flooding the body with colloidal particles, so that the reticulo-endothelial system would be so overwhelmed engulfing the particles that the phage might escape capture. Dr. Merril and his coworkers did not pursue that approach at the time as there was very little demand for an alternative antibacterial treatment such as phage therapy in the 1970s, given the numerous and efficacious antibiotics available.
Subsequently, however, numerous bacterial pathogens of great importance to mankind have become multi-drug resistant (MDR), and these MDR strains have spread rapidly around the world. As a result, hundreds of thousands of people now die each year from infections that could have been successfully treated by antibiotics just 4-5 years ago. [See e.g. C. Kunin, "Resistance to Antimicrobial Drugs--A Worldwide Calamity", Annals of Internal Medicine, 1993;118:557-561; and H. Neu, "The Crisis in Antibiotic Resistance", Science 257, 21 Aug 1992, pp. 1064-73.] .In the case of MDR tuberculosis, e.g., immunocompromised as well as non-immunocompromised patients in our era are dying within the first month or so after the onset of symptoms, despite the use of as many as 11 different antibiotics.
Medical authorities have described multi-drug resistance not just for TB, but for a wide variety of other infections as well. Some infectious disease experts have termed this situation a "global crisis". A search is underway for alternative modes and novel mechanisms for treating these MDR bacterial infections.
Bacteriophage therapy offers one possible alternative treatment. Learning from the failure of bacteriophage therapy in the past, the present inventors have discovered effective ways to overcome the major obstacles that were the cause of that failure.
One object of the present invention is to develop novel bacteriophages which are able to delay inactivation by an animal's host defense system, any component of which may be diminishing the numbers or the efficacy of the phage that have been administered.
Another object of the present invention is to develop a method for treating bacterial infectious diseases in an animal by administering to the animal an effective amount of the novel bacteriophage, and by an appropriate route of administration.